/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package co.elastic.clients.util;

import javax.annotation.Nullable;

/**
 * A union that is open, i.e. non-exhaustive, where new variants can be defined on the server using extension plugins.
 *
 * @see TaggedUnion
 */
public interface OpenTaggedUnion<Tag extends Enum<?>, BaseType> extends TaggedUnion<Tag, BaseType> {

    /**
     * Get the actual kind when {@code _kind()} equals {@code _Custom} (plugin-defined variant).
     */
    @Nullable
    String _customKind();
}
